Ultrathin porous graphitic carbon nanosheets activated by alkali metal salts for high power density lithium-ion capacitors

Graphitic carbons with reasonable pore volume and appropriate graphitization degree can provide efficient Li+/electrolyte-transfer channels and ameliorate the sluggish dynamic behavior of battery-type carbon negative electrode in lithium-ion capacitors (LICs). In this work, onion-like graphitic carbon materials are obtained by using carbon quantum dots as precursors after sintering, and the effects of alkali metal salts on the structure, morphology and performance of the samples are focused. The results show that alkali metal salts as activator can etch graphitic carbons, and the specific surface area and pore size distribution are intimately related to the description of the alkali metal salt. Moreover, it also affects the graphitization degree of the materials. The porous graphitic carbons (S-GCs) obtained by NaCl activation exhibit high specific surface area (77.14 m(2).g(-1)) and appropriate graphitization degree. It is expectable that the electrochemical performance for lithium-ions storage can be largely promoted by the smart combination of catalytic graphitization and pores-creating strategy. High-performance LICs (S-GCs//AC LICs) are achieved with high energy density of 92 Wh.kg(-1) and superior rate capability (66.3 Wh.kg(-1)at 10 A.g(-1)) together with the power density as high as 10020.2 W.kg(-1).